Uncertainty cuts both ways highlights University of Bristol’s Stephan Lewandowsky – if your preferred estimate is at the low end of a range, you’re neglecting similarly likely high end estimates. Image credit: University of Bristol

These messages could hardly be any clearer, but still some of us remain uncertain on the need to act. The best argument for waiting until we’re more certain to act is that if climate change turns out to be harmless, our efforts to fight it will be wasted. Even simple things like current weather are enough to sway our opinions, and when uncertain it’s always tempting to feel like we don’t need to do anything. But that’s the wrong reaction to uncertainty on climate change, according to psychologist Stephan Lewandowsky from the University of Bristol, UK.

A measurement taken on a shaded back deck in Oswego, Oregon on July 29, 2009 at 6pm. 41.3°C or 106.34°F – just one example of increasingly common hot summers in the Northern Hemisphere. Image copyright Sean Dreilinger used via Flickr Creative Commons licence.

Human influence on climate is set to make otherwise unusually hot summers in the Northern Hemisphere more frequent, even if the current warming slowdown continues. That finding, from a new study by Youichi Kamae from the National Institute for Environmental Studies in Tsukuba, Japan, and his colleagues, could now heat up climate talks. “The recent hot summers over land regions and the climate hiatus have opposite effects on ongoing global negotiations for climate policies,” Youichi underlined. “The findings of this study can have significant implications for policy makers.”

Over the past 15 years, growing ‘anthropogenic’ or human-emitted CO2 hasn’t turned into significant average temperature rises on the Earth’s surface. The top levels of the oceans haven’t warmed significantly either, even though heat is still building up deeper down. However in that time sometimes deadly hot summers have become more common in Earth’s northern half. It’s not clear how that’s happening without average temperatures increasing faster. One possible part of the explanation could be a fast response to greenhouse gas emissions that Youichi and other scientists had previously found. “The fast response over can largely be interpreted as direct land surface warming due to CO2,” Youichi told me.

The odds that yields of maize will fall by a tenth over the next 20 years have shortened from 1-in-200 to 1-in-10. Image copyright Raman Sharma, used via Flickr Creative Commons license.

With the next two decades set to see a stronger increase in demand for food than the rest of the 21st century, declining harvests would cause some serious problems. Right now crop yields are growing, but could climate trends cause them to fall by a tenth, say, over the next 10-20 years?

That’s the question David Lobell from Stanford University in California and Claudia Tebaldi from the US National Center for Atmospheric Research in Boulder, Colorado have tried to answer. They find that if the world wasn’t warming, the chance of yields decreasing by a tenth over the next 20 years would be less than 1-in-200. However, climate change has made shrinking yields more likely, shortening the odds to a 1-in-10 chance for maize and a 1-in-20 chance for wheat.

“It was surprising to see how likely it is nowadays for climate trends to significantly cut into yield progress,” David told me. “It is still more likely than not that climate will be a slight drag on progress instead of a major factor. But we can’t rule out a major slowdown, and that means we should probably think through that type of scenario to figure out how to prepare for it.”

Such near-future climate forecasts are unusual, David underlined. “Longer periods allow the signal of climate change to become clearer compared to natural variability,” he explained. “But it may simply be that most of the initial questions about climate change were about the long timescales, to decide about questions related to energy choices and emissions. Now, a lot of questions are related about how to properly adapt to the changes happening now.”

What will happen to crops is central to David’s interests as associate director of Stanford’s Center on Food Security and the Environment. “I often get asked by governments or the private sector if climate change will threaten food supply in the next couple of decades, as if it’s a simple yes or no answer,” the scientist revealed. “This was especially true of a committee I recently served on focused on social stresses from climate change in the near-term. The truth is that over a 10 or 20 year period, it depends largely on how fast things warm, and we can’t predict that very precisely. So the best we can do is put odds on things.” Read the rest of this entry »

UK Prime Minister David Cameron visiting Dawlish a week after the storms that demolished the sea wall that supported the train line. Image copyright Number 10, used via Flickr Creative Commons license.

Taking the train along the Devon, UK, coast earlier this week I was hypnotised by the lapping waves I saw through the window, and their concealed power. On such a sunny day, the rail journey through Dawlish is perhaps the most beautiful I’ve been on. But in February its ocean-hugging route became its downfall, when storms demolished the sea wall it rests on. Now, thanks to 300 fluorescent-jacket clad workers who performed £35 million worth of repairs, the dangling tracks I saw on TV news are a fading memory. It’s an impressive achievement, but could we afford it if – due to climate change, for example – such ‘orange armies’ had to do battle more often?

The significance of that question was emphasised by Chris Field from Stanford University in California, when I saw him talk recently. Highlighting that all parts of the world are vulnerable to climate change, Chris showed the below image of New York City in 2011, during Hurricane Sandy. “The existing climate created a situation that caused over $50 billion in economic damage for a region of the world that had a vast amount of economic resources and had a response plan in place,” he underlined. “It just wasn’t a plan that was up to the challenges that they faced.” If climate change causes more $50 billion-damage events, can we afford that?

If New York can be taken unaware by Hurricane Sandy, what happens elsewhere, when sea level’s higher? Image credit: Chris Field/IPCC

Just before the ocean crippled the south-west UK’s rail services, Jochen Hinkel from the Global Climate Forum in Berlin, Germany, and his team were answering a similar question. In a paper published in the Proceedings of the National Academy of Sciences of the USA in February, Jochen looked at coastal flood damages from projected sea level rise. When I therefore asked him about his work, he was quick to put climate change-driven sea level rise’s role in Hurricane Sandy and this year’s UK storms into context. Read the rest of this entry »

A Roman altar with the Sun in its chariot on the left, and Vulcan, the god of fire and volcanoes on the right. The climate gods long favoured the Roman Empire, with Earth’s orbital dance credited for increasing the amount of solar energy falling on Earth at the time. Image copyright: Nick Thompson, used via Flickr Creative Commons License.

Our climate has changed before. It’s something most of us realise and can agree on and, according to Skeptical Science, it’s currently the most used argument against human-caused warming. If such changes have happened naturally before, the argument goes, then surely today’s warming must also be natural. It’s an appealing idea, with an instinctively ‘right’ feel. Nature is so huge compared to us puny humans, how can we alter its course? The warming we’re measuring today must just be a natural fluctuation.

It’s such an appealing argument that at the beginning of the 20th century that’s just what many scientists thought – that humans couldn’t alter Earth’s climate. In the time since, our knowledge has come a long way. We’ve explored space, become able to build the electronics that are letting you read this, and climate science has likewise advanced and benefited from these advances.

So what do we know today that might convince the sceptical scientists of 115 years ago that we’re warming the planet? Recently, Richard Mallett, one of my Twitter friends who describes himself as sceptical about mainstream climate science, made a point that serves as an excellent test of our current knowledge:

@andyextance Climate science should be able to explain the Holocene, Roman, Medieval and current warmings and the cold periods in between.

Of the historical warmings he’s referring to, perhaps the least familiar is the Holocene, which is ironic, as the Holocene is now. It’s the current period of geological time that started at the end of the last ice age, 11,700 years ago. By 1900 scientists would have known the term, but they couldn’t explain why it wasn’t as icey as before.

Three variables of the Earth’s orbit—eccentricity, obliquity, and precession—affect global climate. Changes in eccentricity (the amount the orbit diverges from a perfect circle) vary the distance of Earth from the Sun. Changes in obliquity (tilt of Earth’s axis) vary the strength of the seasons. Precession (wobble in Earth’s axis) varies the timing of the seasons. For more complete descriptions, read Milutin Milankovitch: Orbital Variations. Image credit: NASA/Robert Simmon.

The explanation we have today comes thanks to the calculations Milutin Milanković worked out by hand between 1909 and 1941. Milutin showed that thanks to the gravitational pull of the Moon, Jupiter and Saturn, Earth’s orbit around the Sun varies in three ways. Over a cycle of roughly 96,000 years our path varies between more circular and more oval shapes. The other two ways come because Earth’s poles are slightly tilted relative to the Sun’s axis, which is why we have seasons. The angle of that tilt shifts over a roughly 41,000 year cycle. Earth also revolves around that tilted axis, like a spinning top does when it slows down, every 23,000 years.

This is part three of this profile. Read part one here and part two here.

In response to the revelations of his ongoing research, NASA scientist Jim Hansen has become increasingly active in campaigning to halt climate change over the past decade. Image credit: Greenpeace

By December 6, 2005, NASA Goddard Institute of Space Studies’ (GISS) temperature record was already sending a clear message: worldwide, 2005 would likely be the warmest year so far. For GISS director Jim Hansen, speaking to the annual American Geophysical Union conference, arguably the world’s largest environmental research meeting, it seemed fair to reveal. For several listening journalists it was newsworthy enough for them to cover Jim’s talk. But it would anger some of Jim’s colleagues at NASA headquarters enough to try to stop him talking to the media. In the process they’d drag him outside the world of pure research he was most comfortable in. “The undue influence of special interests and government greenwash pose formidable barriers to a well-informed public,” Jim would later write about the situation. “Without a well-informed public, humanity itself and all species on the planet are threatened.”

The comments came during a lecture in honour of Dave Keeling, the CO2 tracking pioneer, who’d died of a heart attack in June that year. Soothing Jim’s hesitation, Dave’s son Ralph stressed he was continuing the work of his father, who had even been discussing one of Jim’s papers minutes before his death. And so Jim had brought together evidence showing that Earth’s climate was nearing a ‘tipping point’ beyond which it will be impossible to avoid dangerous changes. However, warming from 2000 onwards might still be kept below the 1°C level that Jim at that time considered hazardous if CO2 levels in the air were held at about 450 parts per million (ppm). Emissions of other greenhouse gases would also need to be significantly reduced. The message was clear: how we get our energy would must change, mainly by shifting away from coal and the vast volumes of CO2 burning it produces.

NASA headquarters was already reviewing all publicity on climate change research, but the latest coverage would force it into even more severe action. The following week it laid out new restrictions on Jim’s ability to comment publicly, and the global GISS temperature record was temporarily taken off the internet. Prominent amongst those setting the new conditions was NASA’s new head of public affairs, appointed by George Bush’s administration, David Mould. His previous jobs included a senior media relations role at the Southern Company of Atlanta, the second largest holding company of coal-burning power stations in the US. Only one company had donated more to the Republican Party than the Southern Company during George Bush’s 2000 election campaign: Enron. Read the rest of this entry »

Jim Hansen giving testimony at a US Congressional hearing in 1988, where he’d declare 99% certainty that humans are changing the climate. Image credit: NASA

“It’s time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here.” It’s a comment that wouldn’t sound out of place today, but Jim Hansen made it 26 years ago, on June 23, 1988, amid record 38°C temperatures in Washington DC. Jim said it to reporters after telling a Congressional hearing he was 99% certain the world is getting warmer thanks to human-made greenhouse gases.

Jim’s 1980s media bombshells led journalist Robert Pool to liken him to a religious ‘witness’, ‘someone who believes he has information so important that he cannot keep silent’. However, he still felt shy and awkward, preferring to immerse himself in pure science, and so would turn down almost all invitations to speak out for another decade. Jim’s efforts during that period would then help build even stronger evidence on global warming. But with extra motivation provided by clashes with the US government and the arrival of his grandchildren he would return to bear witness more forcefully than ever.

Before his self-imposed media ban Jim would make headlines one more time in 1989, after giving written evidence to a hearing convened by then US senator Al Gore. The testimony reaching the hearing had been altered by the White House to make his conclusions about the dangers of global warming seem less certain. When Jim sent the future vice-president a note telling him this, he alerted the media, turning their scheming into the lead story across all TV networks that evening. John Sununu, aide to then president George H. W. Bush, would then try to get Jim fired for his troubles. But Republican senator John Heinz intervened on Jim’s behalf, and he kept his job.